Magnetic disks are produced through various steps, including working, sorting, conveying, etc. For instance, in the case of magnetic disks made of aluminum, round plates (disks) of aluminum are plated and then polished.
However, since disks may differ in substrate thickness and plating thickness, finished disks do not necessarily have the same thickness.
On the other hand, the polishing of disks can be effectively conducted when they have the same thickness. For this purpose, it is important that plated disks (semi-finished disks) are sorted depending on their thickness.
For sorting semi-finished disks, various methods and apparatuses are already reported.
For instance, Japanese Patent Laid-Open No. 62-225283 discloses a disk-sorting apparatus comprising (a) a supply means for supplying plural types of disks having different diameters and thickness to predetermined positions in plural numbers per each type; (b) a support means for supporting one of plural types of disk-holding members in an upright manner, the disk-holding members being positioned corresponding to plural types of the disks; (c) a supply manipulator disposed between the supply means and the support means for conveying one disk from the supply means to the support means in an upright manner; (d) a means for measuring a thickness of each disk conveyed to the support means; (e) a means for receiving each disk, which is sorted into a predetermined rank depending upon measurement results, from the support means in an upright manner; and (f) a sorting manipulator disposed between the support means and the receiving means for transferring a measured disk from the support means to one portion of the receiving means in an upright manner.
Japanese Patent Publication No. 63-56831 discloses a sorter comprising trays for containing parts, a transfer means for taking out each part from each tray by holding it by a chuck and transferring it to a supply means intermittently, a conveying means for conveying each part to a means provided with two pairs of fingers for regulating a position of each part, a measurement means for measuring a size of each part, and ranked empty trays for receiving measured trays depending upon their measurement results. The sorting of each part into each ranked tray is carried out by a robot having X-, Y- and Z-axis arms.
In the sorting process in which disks are measured with respect to thickness and sorted depending upon their thickness, the damaging and deformation of disks should be prevented while keeping high measurement and sorting speeds. Further, from the aspect of operability, it is desirable that thickness ranges in which disks are ranked and the number of ranks can be easily changed.
In the disk-sorting apparatus of Japanese Patent Laid-Open No. 62-225283, since each disk is gripped, it is likely to be damaged. Also, since each means such as a measurement means and a sorting manipulator moves, high-speed measurement and sorting cannot be achieved.
In the sorter of Japanese Patent Publication No. 63-56831, since a part is taken out from the tray by a chuck and conveyed intermittently without any cover, it is likely to be damaged, and it takes much time to adjust the position of a part. Namely, this sorter is not satisfactory with respect to damage prevention and operation speed.